Fluid-flow system, device and method

ABSTRACT

Methods, devices, and systems are disclosed for combining fluids of different pressures and flow rates in, for example, gas gathering systems, gas wells, and other areas in which independently powered compressors or pumps are not desired.

RELATED APPLICATION DATA

The instant application claims priority to prior provisional applicationNo. 60/682,291, filed May 18, 2005.

BACKGROUND

In many areas involving fluid-flow, it is desirable to combine twostreams of fluid that have different pressures. An example of such asystem is a well that produces natural gas.

The gas that comes from a flowing well is typically passed through aseparator where liquids “drop out” of the gas stream. Those liquids arevery valuable; they contain a high BTU content. The liquids are removedfrom the separator and placed in a large liquid storage tank, and theremaining gas is removed from the separator in a gas line. The liquidstorage tank generates vapor that is slightly above atmosphericpressure. That vapor must be compressed to a pressure closer to the gasleaving the separator (which is expensive) or that vapor must be ventedto the atmosphere. In some cases, the volume of vapor is sufficient thata flare can be used; however, flaring of the vapor usually results inincomplete combustion and undesirable by-products, and that results inpollution. It is also a waste of the energy content of the vapor.

Therefore, there is a need for a method, system, and device, which cantake fluid of a first pressure (for example, high pressure gas comingfrom a separator) and combine into that first-pressure-fluid a secondfluid of lower pressure (for example, the vapor from a liquid storagetank) while avoiding the normal costs of compression of the second,lower pressure gas.

In some other examples, there are multiple wells in an oil and/or gasproducing field. Those wells may be producing gas at differingpressures. To put those multiple wells (each producing at a differentpressure) on an individual gas transmission line requires pressurerelease from the higher pressure flows or compression of the lower linepressure flows. Again, the cost of compression is high; either anelectric or gas-fired engine driven compressor is needed. Whether thecost is in lost gas, the cost of electricity, or the cost of the fuelneeded to run the compressor, it is undesirable. Therefore, there is aneed to combine flows of fluids having different pressures into anindividual fluid flow line without the traditional compression orpumping steps.

SUMMARY

According to a first example of the invention, a gas gathering system isprovided comprising: a first well; a first flow line of gas from thefirst well; a first separator connected to the first flow line; a firstseparated gas flow line connected to a first input of a means forcombining at least two gas flows having different pressures; a secondwell; a second flow line of gas from the second well; a secondseparation connected to the second flow line; a second separated gasflow line connected to a second input of the means for combining;wherein the means for combining comprises a first input volume and asecond input volume; and a pressure differential between the first inputvolume and the second input volume causes a portion of the first inputvolume to be combined with a portion of the second input volume at anoutput volume.

In another example of the invention, a gas gathering system is providedthat comprises: a first input of gas at a first pressure; a second inputof gas at a second pressure, the first pressure being higher than thesecond pressure; a means for combining the first and the second inputsof gas; wherein the means for combining uses pressure differencesbetween the first input of gas and the second input of gas to power themeans for combining. At least one such system further comprises agas/fluid separator receiving gas and fluids from a well; wherein thefirst input of gas comprises gas from the separator, and a liquids tank,receiving liquids from the separator, and wherein the second input ofgas comprises vapor from the tank.

In still another example of the invention, an apparatus is provided thatis useful in combining at least two fluids of differing pressures. Theapparatus comprising: a housing; a first rotor within the housing; asecond rotor within the housing, the first rotor engaging the secondrotor and both the first and the second rotors engaging the housing; athird rotor within the housing and engaging the first rotor; a fourthrotor within the housing and engaging the second rotor, the third rotorengaging with the fourth rotor and both the third and the fourth rotorsengaging the housing; wherein the first and the second rotors define afirst input volume; wherein the third and the fourth rotors define asecond input volume; wherein the first and the third rotors define afirst output volume; and wherein the second and the fourth rotors definea second output volume.

In at least some such examples, at least two rotors engage each other ina sealing arrangement and are substantially the same size. In otherexamples, a first pair of the rotors is larger than a second pair of therotors. In many examples, the rotors are mounted on bearings aroundfixed shafts; while, in further examples, at least one rotor is fixed tothe shaft of the rotor.

In some examples, the housing comprises a substantially cylindricalshape and has sealing surfaces that are arranged to seal with therotors. Inputs are also substantially normal to the axis of the housing.In further examples, the housing comprises inputs substantially parallelto the axis of the housing.

In yet another example of the invention, a rotor is provided that isuseful in an apparatus for combining at least two fluids of differingpressures. The rotor comprises: a set of protrusions; a set of recessesbetween the protrusions; wherein the protrusions comprise sealingsurfaces, at least a portion of the sealing surface comprises a portionof a first circle, the recesses comprise sealing surfaces, at least aportion of the sealing surface comprises a portion of a second circle,the first circle and the second circle are tangential, the first circleand the second circle each have centers located on a circle having acenter on an axis of the rotor. Some such rotors form a substantiallycylindrical void in their center and rotate on bearings about a shaft.Other such rotors are fixed to a shaft, and the shaft rotates.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1D are a schematic of an example of the invention.

FIG. 2 is a perspective view of an example of the invention.

FIG. 3 is a side view of an example of the invention.

FIG. 4 is a perspective view of an example of the invention.

FIG. 5 is a side view of an example of the invention.

FIGS. 6A-6H are perspective views of examples of the invention.

FIG. 7 is an exploded view of an example of the invention.

FIGS. 8-11 are sectional views of examples of the invention.

FIG. 12 is a perspective view of an example of the invention.

FIG. 13 is a sectional view of an example of the invention.

FIG. 14 is a perspective view of an example of the invention.

FIG. 15 is a schematic of an example of the invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

FIG. 1A illustrates an example of the invention in which a flowing well10 sends gas to separator 12 over flow-line 11. From separator 12 (of acommon design known to those of skill in the art), liquids pass throughliquid transfer line 15 into storage tank 13. Gas passes from separator12 onto gas flow line 17. Vapor from liquid storage tank 13 is removedfrom liquid storage tank 13 via vapor flow line 19. The pressure and gasflow line 17 is higher than the pressure in vapor flow line 19.Therefore, combiner unit 26 is provided to combine the fluid flow fromgas flow line 17 and vapor flow line 19 into a single combined gas flowline 28.

Vapor flow line 19 is passed through vapor flow meter 14 and enterscombiner unit 26 at valve 21. Gas flow line 17 is passed through gasflow meter 16 and enters combiner unit 26 at valve 18 b. Valve 18 aopens and closes in response to a pressure transmitter located in line19 (not shown), thereby controlling whether the higher pressure gaspasses directly through combiner unit 26 to gas flow line 28 or whetherit will be combined with vapor from vapor flow line 19. Valves 18 a, 18b, 18 c, 18 d, 18 e, and 21 comprise manually operated valves (in someexamples), which remain in an open position until it is necessary toperform maintenance or repairs; then, they are closed to isolate unit26. For example, if valve 18 a is closed, and valves 18 b and 18 c areopen, gas flows from gas flow line 17 through solids filter 20 and intocombiner component 22 (also sometimes referred to herein as a means forcombining). When valve 21 is open, vapor flowing at a low pressure fromvapor flow line 19 also enters combiner component 22. In some otherexamples, one or more of valves 18 a-18 e or 21 compriseautomated-operation valves.

Combiner component 22 combines the gas flow and vapor flow, resulting inan individual flow that is at a pressure between the pressure of the gasand the vapor, and that individual flow is passed through valve 18 eonto combined gas flow line 28 by the opening of valve 18 d with valve18 a closed.

In at least some alternative embodiments, filter 20 is not used.Likewise, in some alternative embodiments, vapor flow meter 14 and/orgas flow meter 16 are not used. A pressure release valve 19 is seenconnected to liquid storage tank 13 for the purpose of venting excesspressure build-up in liquid storage tank 13 either to air, a traditionalcompressor, or a flare (in the event of a problem downstream of liquidstorage tank 13).

Referring now to FIG. 1B, another example embodiment of a combiner unit26 is seen in which at least two flow lines 11 a and 11 b fromindependent wells (not shown) feed into solids filters 20 a and 20 bthrough valves 10 a and 10 b. Valves 110 c and 110 d allow communicationbetween flow lines 11 a and 11 b in an open state and isolates flowlines 11 a and 11 b in a closed state. Check valves 110 e and 110 fprevent back flow.

Gas flow lines 17 a and 17 b are fed through flow meters 14 a and 14 brespectively into inputs Ia and Ib of combiner component 22. Gas fromdifferent wells may flow at different pressures and/or flow rates, andthe flow from any particular well may fluctuate greatly. For example,wells having pumping mechanisms and/or having pressure-sensitive valvesthat open upon the well pressure reaching a particular level allow flowuntil the well pressure drops below a different level; they then closethe well again, allowing pressure to build. Because of this, without acombiner component 22, it is difficult and costly to take the productionof multiple wells and combine them into a single line 28. Furthermore,the production from the lesser wells is limited beyond its otherwiseproducing capability by the production from the greater wells; and,further still, the pressure the artificial lift mechanism must overcomeis higher. Combiner component 22 takes the flows at inputs Ia and Ib andcombines them into a plurality of outputs to form flow line 28. In theillustrated example, two outputs, Oa and Ob, are substantially the samepressure and flow rate at a given moment in time and are connectedtogether (e.g., by a joint, manifold, or other form of or means forcombining substantially similar flows).

Valves 110 a, 110 b, and 110 c, allow a bypass of filters 20 a and 20 band of combiner component 22, when valves 110 a and 110 b are in aclosed state and valve 110 c is in an open state. In such a case, thehigher pressure and flow rate line 11 a or 11 b will dominate the flowinto flow line 11 and then into flow line 28. In those systems in whichthe flow rates and pressures of the wells fluctuate, the flow line thatdominates will fluctuate between line 11 a and 11 b. However, such anarrangement allows for maintenance of the filters 20 a and 20 b and ofcombiner component 22.

FIG. 1C illustrates a further example embodiment of a combiner unit 26in which flow line 128 feeds into solids filter 20 a through valves 311a and 311 b, and flow line 128′ feeds into solids filter 20 b throughvalves 311 c and 311 d. When valve 311 a is in a closed state, there isno flow from line 128. When valve 311 a is in an open state, flow occursthrough bypass line 311, if valve 311 e is in an open state and valve311 b is in a closed state, through T-joint 310. There is no flow inbypass line 311 when valve 311 e is in a closed state and valve 311 b isin an open state, and flow then continues into solids filter 20 a.Similarly, flow line 128′ is fed into solids filter 20 b when valves 311c and 311 d are in open states while valve 311 f is in a closed state,and flow line 128′ bypasses filter 20 b through T-joint 310′ when valve311 d is in a closed state and valve 311 f is in an open state. Valve218 is closed in the bypass state of the system.

Control system 209 monitors meters 210 a and 210 b through signal paths202 a and 202 b. In the illustrated example, meters 210 a and 210 bcomprise differential pressure meters. Other examples utilize othermeans for measuring pressure that will occur to those of skill in theart. Control system 209, through signal paths 242 a and 242 b, operatescontrol valves 223 a and 223 b (based on inputs from meters 210 a and210 b, respectively), to control input to combiner component 22. Inconjunction with valves 203 a and 203 b, which are also controlled fromcontrol system 209 (through signal paths 243 c and 243 d), valves 223 aand 223 b bypass combiner component 22 under the following conditions(among others): (i) when both inlet streams 128 and 128′ have pressuresufficient to enter line 300 without negative effect on productionsources, (ii) line 128 or 128′ does not flow, or (iii) during periods ofroutine maintenance or repair.

In other situations, the flow from filter 20 a enters an input ofcombiner component 22 and the flow from filter 20 b enters another inputof combiner component 22. As previously mentioned, their pressures andflow rates are combined into a single flow line 300 through outputs tiedto lines 214 and 214′, through joint 216 (here, a cross), valves 218,and shut off valve 205.

Referring now to FIG. 1D, a further alternative is seen in which a gasflow line 401 (e.g., of an individual well at 25 psi) and a second gasflow line 403 (for example, a gas gathering system trunk line at 500psi) are input into combiner unit 26 (e.g., as seen in FIGS. 1A, 1B,and/or 1C), when valve 405 is in a closed state. The combiner unit 26(also referred to as a means for merge unit and/or a means for gasboosting) combines the pressures and flow rates of the flow lines 401and 403 into flow line 409 (resulting in a combined pressure between 500psi and 25 psi) which is then fed as an input to compressor 412.Compressor 412 steps up the pressure in flow line 411 to a higherpressure (for example, main line pressure).

In many situations, the higher pressure and volume of the main line areenough that the compressor 412 is unneeded. In such a situation, output411 becomes an input to a system of the same basic layout as seen inFIG. 1D. The main line is line 403 and the gathering system output isline 401. In some such examples, the pressure and flow rate of lines 401and 403 will be such that there will be a negligible drop in pressurebetween lines 403 and 411 while still combining the volume of line 401into compressor 412, which compresses the pressure to be used by otherdownstream systems 413 and/or 415.

Referring now to FIG. 2, an example of combiner component 22 (alsosometimes referred to as a means of combining) of FIGS. 1A-1D is seen.For example, gas flow line 17 (FIG. 1A) is connected to bottom input 17i and vapor flow line 19 (FIG. 1A) is connected to top input 19 i. Thetwo fluid flows from gas flow line 17 and vapor flow line 19 arecombined in combiner component 22 (as will be explained in more detailbelow) and output through outlets 29 a and 29 b. The flow from outlet 29a is at substantially the same pressure and rate as in outlet 29 b andthe two are combined (for example, through a direct connection such as ajoint or manifold) and then applied (in the example of FIG. 1A) throughoutlet line 29 and control valve 18 e to combined gas flow line 28.

In FIG. 3, an end-view of the example combiner component 22 of FIG. 2 isseen in which vapor from vapor line 19 enters through top inlet 19 i toform inlet volume VI₁ (defined between rotors R1 and R2 and innerhousing pipe 32). Gas flows from flow line 17 through bottom inlet 17 iinto the second inlet volume VI₂ (defined between rotors R4 and R3 andinner housing pipe 32).

In operation, the high pressure in inlet volume VI₂ causes rotor R4 torotate clockwise while rotor R3 rotates counter-clockwise. Likewise,rotor R1 rotates counter-clockwise while rotor R2 rotates clockwise.Rotor protrusions P seal against inner housing pipe 32 as they rotateand again seal as they mesh with their neighboring rotors. Therefore,fluid in inlet volumes VI₁ and VI₂ are passed between protrusions P andinner pipe housing 32 into outlet volumes VO₁ and VO₂. When those fluidflows reach outlet volumes VO₁ and VO₂, they combine. In both outletvolumes VO₁ and VO₂, the pressure level is between the pressure level ininlet volumes VI₁ and VI₂. Further, the pressure in VO₁ is about thesame as the pressure in VO₂, and the flow in outlet volume VO₁ is equalto the flow in outlet volume VO₂. Therefore, outlets 29 a and 29 b canbe directly combined (for example, through a simple joint or manifold).

Referring now to FIG. 4, a perspective view of an example is seen of arotor 40, which is useful in the example of FIG. 3 for rotors R1, R2,R3, and R4. Rotor 40 comprises a member having substantial symmetryabout an axis 42 having ten protrusions P1-P10. Rotor 40 also includes acylindrical void 44. In at least some examples, rotor 40 comprisessteel, ceramic, and/or other materials that will occur to those of skillin the art.

In some examples, the outer diameter shape of rotor 40 is formed by anEDM machine. As used herein, EDM stands for electrical dischargemachining, a process that is known to those of skill in the art. In someexamples, the cylindrical void 44 is also formed by an EDM process. Inother examples, cylindrical void 40 is bored and the outer shape is cutby an EDM process. Still other examples of methods of forming rotorsinclude CNC (Computer Numerical Control) machining, extrusion, and othermethods that will occur to those of skill in the art.

While the example of FIGS. 3 and 4 shows rotors with ten protrusions,the invention is not limited to such an example. Other numbers ofprotrusions are useful according to other examples of the invention, aswill be explained in more detail below.

Referring to FIG. 5, a cross-sectional view of an example rotor 50 isseen having twelve protrusions P1-P12. Each of protrusions P1-P12 isformed according to a set of circles, each of which has its centerC1-C24 located on a larger circle C0. C0 has its center on axis 52 ofrotor 50.

Referring again to FIG. 3, as the rotors R rotate, the protrusions Pseal with the recess between protrusions in adjacent rotors. In exampleembodiments in which the relationship of the number of protrusions tothe diameter of circle C0 is maintained, the protrusions P engage in asubstantially non-sliding manner when two rotors are rotated inconnection with each other. Lack of a sliding engagement provides thefollowing benefits: lack of friction, extrusion of the material in thevolume (rather than compression), and reduced wear. While, in some otherexamples, non-circular shapes may be used, curved shapes (and, inparticular, a circular shape) provide advantages of sealing the outervolumes VI₁, VI₂, VO₁, and VO₂, from each other and from the interiorvolume defined by the four rotors R1, R2, R3, and R4.

Referring still to FIG. 3, the more protrusions that exist, the betterthe seal is between the protrusions P and inner pipe housing 32.However, given the same diameter, the more protrusions P that exist, thesmaller the volume is that can be moved per rotation from an inletvolume to an outlet volume (for example, VI₁ to VO₁). Further examplesof rotors useful according to other examples of the invention are seenin FIGS. 6A-6H, where a cylindrical void is not shown. There is notheoretical limit to the number of protrusions in various examples ofthe invention.

Referring again to FIG. 3, rotors R1, R2, R3, and R4 are shown solid forsimplicity; however, in reality, the cylindrical void of each of therotors includes a shaft and a bearing member 62, as also seen in FIG. 2.In the examples of FIGS. 2 and 3, bearing member 62 comprises aball-bearing assembly (although other means for providing low frictionrotation between a fixed shaft and a rotor also are useful in furtherexamples of the invention). Still further, in other examples, rotors Rdo not spin around a shaft; rather, they are integrally formed with orconnected in a fixed manner to the shaft, and the shaft spins onbearings mounted in the housing or an end plate. Further means ofproviding for rotational motion of rotors R will occur to those of skillin the art in view of the present disclosure that are within the scopeof the present invention.

Even further, although the illustrated examples show rotors ofsubstantially the same size, in alternative examples, a pair of rotorsis of smaller diameter than another pair of rotors allowing fordifferences in the volume handled by the different inputs.

Referring now to FIG. 7, an example embodiment is seen in an explodedview in which shafts 74 a-74 d each have two bearings. For example,shaft 74 a has bearing 72 a and 72 a′; shaft 74 b has bearings 72 b and72 b′, etceteras. Rotors 70 a-70 d rotate on the bearings 72 a-72 d and72 a′-72 d′. Shafts 74 a-74 d are fixed.

Rotors 70 a-70 d form inlet and outlet volumes in cooperation with eachother and block 76 in which one inlet port 78 and one outlet port 80 areseen. The other inlet port is on the bottom of block 76 (not shown) andthe other outlet port is on the fourth side of block 76 (also notshown). When assembled inside of block 76, shafts 74 a-74 d are mountedin end plates 82 and 82′ through holes 84 a-84 d and 84 a′-84 d′.

In at least one example method of assembly, shims (not shown) arewrapped around rotors 70 a-70 d to set a consistent clearance betweenthe block 76 and rotors 70 a-70 d. Dowel-pin holes (also not shown) arethen drilled through end plates 82 and 82′ and into block 76. The shimsare then removed and the apparatus is re-assembled with the correctclearance, using the dowel-pin holes as a guide.

Referring now to FIG. 8, a sectional view of an example of a shaftuseful in the example of FIG. 2, 3, or 7 is seen. According to theexample of FIG. 8, shaft 80 includes a shaft body 83 including a firstoil path 84 and a second oil path 84′. Lubricated surface 86 of shaft 80receives lubrication through oil paths 84 and/or 84′ through an oilfitting 88, which includes oil port 90. Threads 92 allow shaft 82 to beconnected in a fixed manner with a nut (not shown) outside of end plates82 and 82′ (FIG. 4). O-ring 94 is used to seal shaft 80 with end plates82 and 82′; shoulder 96 butts up against end plates 82 and 82′ providingan end-seal to prevent leakage of lubrication from lubricated surface86.

FIG. 9 shows a cross-section of an example of a babbit bearing housing98 that is useful as a bearing in various examples of the invention. Asubstantially cylindrical body 100 includes a shaft hole 102. Withinshaft hole 102, a babbit material cavity 104 is formed to receive babbitmaterial, which is not shown in FIG. 9. Also included in shaft hole 102is an O-ring seal groove 106.

In some embodiments of the invention, the seal between rotors or betweena rotor and the non-rotating housing or block is enhanced by a means forsealing (e.g., a seal member or blade) that extends from eachprotrusion. An acceptable example of such a means for sealing is seen inFIG. 10A, which is a cross-section of a rotor R having protrusions P,which include a longitudinal blade 108 and a pin 116. When a protrusionis not either mated in the recess 112 between two protrusions P ofanother rotor or engaged against the housing, blade 108 is in anextended position 113 from the bottom of channel 111 and is biased by anO-ring 118, which is held in a groove 119 of rotor 70. As seen in FIG.10B, when a protrusion (here the middle protrusion) engages anotherrotor, blade 108 is compressed into protrusion P and pin 116 compressesO-ring 118, slightly. Blade 108 may still extend slightly fromprotrusion P, as discussed below. For simplicity, stop surfaces used tohold blade 108 in protrusion P are not shown but will occur to those ofskill in the art. In some examples, blade 108 is flat, as seen; infurther examples, the extended surface of blade 108 is curved.

Referring now to FIG. 11, a cross-sectional view of an example assembledshaft bearing, and rotor, is seen. The top 110 of protrusion P of rotor70 in the example shown is in a dashed line; blade 108 rides between thebottom of blade channel 111 in protrusion P and an extended position atthe top-most travel of blade 108. As mentioned previously, blade 108 ispositioned in a biased manner by pin 116 and a biasing means (forexample, an O-ring) 118 that is held in a groove 120 and closed by anend seal 122. As briefly described earlier with reference to FIG. 8, anut 126 backed by washer 124 fixes shaft 80 against end plate 82′.

During operation, as rotor 70 spins around bearings 98, and (as bothbearings spin around shaft 80) a lubricant (e.g., oil) is suppliedthrough lubrication paths 84 and 84′ under babbit material (not shown)in cavity 104, lubricant moves between bearings 98 to substantially filloil chamber 128 and to flow from shaft 84′ to shaft 84 (or the reverse).The presence of a fluid in contact bearing 98 and/or rotor 70 also actsas a coolant of the member with which the coolant is in contact.

Referring still to FIG. 11, the top of blade 108 extends against thesidewall of block 76 (or, for example, inner pipe 32 of FIG. 3) to forma seal. There may be a very slight gap without blade 108, in someexamples. In some examples that do not use a blade, the motion of theprotrusion in close proximity to block 76 is believed to create a“labyrinth seal” or “sonic seal” due to turbulence. In some examples ofthe invention in which a labyrinth seal might not be relied on, blade108 adds an additional seal. As rotor 70 turns to engage another rotor,blade 108 compresses within protrusion P. In further examples, neither alabyrinth seal nor a means for sealing (such as blade 108) is used.

Referring now to FIG. 12, an alternative for block 76 of FIG. 7 is seen.Block 130 includes ports that are in parallel to the axes of rotation ofthe rotors. By contrast, in FIG. 7, block 76 is ported with inlet andoutlet ports 78 and 80, which are normal to the axes of rotation ofrotors 70 a-70 d. Specifically, in block 130 of FIG. 12, inlet ports 132and 132′ are provided opposite each other, and outlet ports 134 and 134′are also opposite each other. Such parallel porting reduces thepotential for axial pressure differentials within any particularpressure volume.

A cross-sectional view of block 130 is seen in FIG. 13 where it is seenthat ports 136, 136′ and 138, 138′, respectively, are larger than in theexample embodiment of FIG. 2 and FIG. 3. There, the circularconfiguration of the housing pipe 32 (which is in place of block 130 ofFIG. 12 or block 76 of FIG. 7) defines smaller volumes. By adjustment ofthe length of the rotor, number of teeth, and diameter of the rotor,adjustment of the volume transferred per protrusion, matching ofvolumes, and varying pressure differentials between inputs isaccommodated.

Referring to FIG. 14, an alternative rotor 140 is seen that includesprotrusions P (as in earlier-described rotors) and that also includes asealing surface 142 that is substantially flush with the bottom of therecess 112 between protrusions P. Such a sealing surface operating inconjunction with a seal in an end plate reduces the chance of the fluid,which becomes trapped between protrusions P, from leaking laterallyaround a protrusion. Groove 146 is cut in the sealing surface 142 toaccept a means for sealing (for example, a ring seal of spring steel, anO-ring, etceteras) to further seal and prevent axial leakage.

Referring again to some examples similar to FIG. 3, once inner housingpipe 32 is assembled with rotors R1, R2, R3, and R4, a flange 33 isslipped over inner pipe housing 32 on both ends and welded to pipe 32. Araised face 35 of slip-on flange 33 is provided onto which O-ring sealchannel 37 is formed. In place of the end plates 82 and 82′ of theembodiment of FIG. 7, a blind flange (not shown) is mated with theslip-on flange 33 and secured with bolts 39 and nuts 39′. O-ring seal 37mates with a complimentary raised face and O-ring groove on the blindflange (not shown).

Referring now to FIG. 15, still a further example of a merge unit system26 is seen in which flow line inputs 500 a and 500 b connect throughvalves 503 a and 503 b and means 505 a and 505 b for measuring pressure(e.g., a differential pressure meter) and then through check valves 509a and 509 b. Bypass lines 511 a and 511 b operate (when valves 513 a and513 b are in an open state, and valves 515 a and 515 b are in a closedstate) and are connected at a joint 517 in output flow line 519. Whenvalves 513 a and 513 b are in a closed state, and valves 515 a and 515 bare in an open state, gas flows through measurement packages 520 a and520 b (each comprising, in at least one example, a pressure measurementdevice 521, a differential pressure measurement device 522, and atemperature measurement device 523). Fluid then passes through valves527 a and 527 b, through check valves 529 a and 529 b and intoseparators 531 a and 531 b, which are monitored by differential pressuremeasurement devices 533 a and 533 b, respectively. Float-actuated valves535 a and 535 b operate to remove liquid from separators 531 a and 531 band pass the liquid to tank 537.

Vapor from separators 531 a and 531 b passes through valves 539 a and539 b into inputs Ia and Ib of combiner component 22, when valves 539 aand 539 b are in an open state. Combiner component 22 combines thepressures and fluid flows as discussed previously into output line 543through valve 545 and measurement package 547. Fluid then flows throughvalves 549 and check valve 551 and into flow line 519. In such anoperation, valves 513 a and 513 b are in a closed state.

In some embodiments, combiner component 22 has shafts that, rather thanbeing fixed, rotate with the rotors. In at least one such embodiment, ashaft is used to turn an electrical generator 553, which produces powerseen in output power lines 559. A rotational shaft of a rotor, in afurther embodiment, is used to turn pumps 561 and 562 having inputvalves 563 a and 563 b and output valves 565 a and 565 b, respectively.Examples of inputs at valves 563 a and 563 b include liquids from oil orwater at a well location to a central location, thus avoiding transportcosts or for reinjection.

A control box 567 operates valves 563 a and 563 b, along with valves 513a and 513 b, in response to measurements from measurement packages 520 aand 520 b and differential pressure measurement devices 533 a, 533 b,and 547. In some embodiments, solids filters similar to those shown inearlier figures are used.

The above description and the figures have been given by way of exampleonly. Further embodiments of the invention will occur to those of skillin the art without departing from the spirit of the definition of theinvention seen to the claims below.

1. A method of combining at least two fluid streams of differingpressures, the method comprising: receiving, into a first volume, afluid of a first pressure; receiving, into a second volume, a fluid of asecond pressure; and combining, in a third volume, a portion of fluidfrom the first volume with a portion of the fluid from the secondvolume, due to a pressure differential between the first volume and atleast the third volume; combining, in a fourth volume, a portion offluid from the first volume with a portion of the fluid from the secondvolume, and communicating the third and the fourth volumes into a singleflow line.
 2. A method as in claim 1 wherein said combining, in a thirdvolume, comprises: capturing the portion of fluid from the first volume;capturing the portion of fluid from the second volume; transporting thecaptured portion of the first volume to the third volume; andtransporting the captured portion of the second volume to the thirdvolume.
 3. A system for combining at least two fluids of differingpressures, the system comprising: means for receiving, into a firstvolume, a fluid of a first pressure; means for receiving, into a secondvolume, a fluid of a second pressure; and means for combining, in athird volume, a portion of fluid from the first volume with a portion ofthe fluid from the second volume, due to a pressure differential betweenthe first volume and at least the third volume; means for combining, ina fourth volume, a portion of fluid from the first volume with a portionof the fluid from the second volume, and means for communicating thethird and the fourth volumes into a single flow line.
 4. A system as inclaim 3 wherein said means for combining, in a third volume, comprises:means for capturing the portion of fluid from the first volume; meansfor capturing the portion of fluid from the second volume; means fortransporting the captured portion of the first volume to the thirdvolume; and means for transporting the captured portion of the secondvolume to the third volume.
 5. A system as in claim 4, wherein saidmeans for capturing the portion of fluid from the first volume comprisesa plurality of rotor protrusions sealing with a non-rotating member,wherein the sealing occurs in the first volume and a plurality of sealedprotrusions defines the captured portion, and said means for capturingthe portion of fluid from the second volume comprises a plurality ofrotor protrusions sealing with a non-rotating member, wherein thesealing occurs in the first volume and a plurality of sealed protrusionsdefines the captured portion.
 6. A system as in claim 4 wherein saidmeans for transporting the captured portion from the first volumecomprises means for rotating the rotor protrusions to an unsealedposition in the third volume, and said means for transporting thecaptured portion from the second volume comprises means for rotating therotor protrusions to an unsealed position in the fourth volume.
 7. Asystem as in claim 6 wherein said means for rotating comprises apressure differential between the first volume and the second volume. 8.A system as in claim 3 wherein said means for communicating comprises afirst fluid output conduit in communication with the third volume, asecond fluid output conduit in communication with the fourth volume,wherein the first and the second output conduits are both incommunication with the single flow line.
 9. An apparatus useful incombining at least two fluids of differing pressures, the apparatuscomprising: a housing; a first rotor within the housing; a second rotorwithin the housing, the first rotor engaging the second rotor and boththe first and the second rotors engaging the housing; a third rotorwithin the housing and engaging the first rotor; a fourth rotor withinthe housing and engaging the second rotor, the third rotor engaging thefourth rotor and both the third and the fourth rotors engaging thehousing; wherein the first and the second rotors define a first inputvolume; wherein the third and the fourth rotors define a second inputvolume; wherein the first and the third rotors define a first outputvolume; and wherein the second and the fourth rotors define a secondoutput volume.
 10. An apparatus as in claim 9 wherein at least tworotors are in a sealing engagement.
 11. An apparatus as in claim 9wherein the rotors are substantially the same size.
 12. An apparatus asin claim 9 wherein a first pair of the rotors is larger than a secondpair of the rotors.
 13. An apparatus as in claim 9 wherein the rotorsare mounted on bearings around fixed shafts.
 14. An apparatus as inclaim 9 wherein at least one rotor is fixed to the shaft of the rotor.15. An apparatus as in claim 9 wherein the housing comprises asubstantially cylindrical shape having sealing surfaces arranged thereinto seal with the rotors.
 16. An apparatus as in claim 15 wherein thehousing comprises inputs substantially normal to the axis of thehousing.
 17. An apparatus as in claim 15 wherein the housing comprisesinputs substantially parallel to the axis of the housing.
 18. A rotoruseful in an apparatus for combining at least two fluids of differingpressures, the rotor comprising: a set of protrusions; a set of recessesbetween the protrusions; wherein the protrusions comprise sealingsurfaces; wherein at least a portion of the sealing surface comprises aportion of a first circle; wherein the recesses comprise sealingsurfaces; wherein at least a portion of the sealing surface comprises aportion of a second circle; wherein the first circle and the secondcircle are tangential; wherein the first circle and the second circleeach have centers located on a circle having a center on an axis of therotor.
 19. A rotor as in claim 18 wherein the rotor forms asubstantially cylindrical void.
 20. A rotor as in claim 18 wherein therotor is fixed to a shaft.
 21. A gas gathering system comprising: afirst input of gas at a first pressure; a second input of gas at asecond pressure, the first pressure being higher than the secondpressure; a means for combining the first and the second inputs of gas;wherein the means for combining uses pressure differences between thefirst input of gas and the second input of gas to power the means forcombining.
 22. A gas gathering system as in claim 18 further comprisinga gas/fluid separator receiving gas and fluids from a well; wherein thefirst input of gas comprises gas from the separator, and a liquids tank,receiving liquids from the separator, wherein the second input of gascomprises vapor from the tank.
 23. A gas gathering system comprising: afirst well; a first flow line of gas from the first well; a firstseparator connected to the first flow line; a first separated gas flowline connected to a first input of a means for combining at least twogas flows having different pressures; a second well; a second flow lineof gas from the second well; a second separation connected to the secondflow line; a second separated gas flow line connected to a second inputof the means for combining; wherein the means for combining comprises afirst input volume and a second input volume; and a pressuredifferential between the first input volume and the second input volumecauses a portion of the first input volume to be combined with a portionof the second input volume at an output volume.